1. Field of the Invention
The invention pertains to the field of flow porometry. More particularly, the invention pertains to a sample chamber for flow porometry.
2. Description of Related Art
Flow Porometry is a technique for measurement of pore diameter, pore distribution and gas permeability. In this technique, a wetting liquid is allowed to spontaneously fill the pores of the sample. The pressure of a non-reacting gas on one side of the sample is gradually increased to empty the pores of the sample and allow gas flow through the empty pores. The differential pressure required to remove liquid from a pore is given by:p=4γ cos θ/D
where p is differential pressure, γ is surface tension of the wetting liquid, θ is the contact angle of the wetting liquid on pore surface and D is pore diameter. The differential pressure of the gas on the sample and the gas flow rates are measured. The differential pressure and gas flow rates through the dry sample with all of its pores open are also measured. The differential pressure yields the pore diameter. The differential pressure and gas flow rates through wet and dry samples yield the largest pore diameter, the mean flow pore diameter, the distribution of gas flow rate over pore diameter and gas permeability. This technique is used in industry for characterization of through pores, which are very important for various kinds of filtration applications in many industries, including chemical technology, biotechnology, food technology and nonwovens.
The PMI Capillary flow porometer (41), shown in FIG. 5, is a flow porometer. It regulates gas pressure, increases gas pressure on samples in small increments, accurately measures pressures and flow rates, automatically executes all operations, and acquires, stores and displays data in many formats. This instrument, with state-of-the-art components, many innovative design features and complete automation is capable of giving highly accurate, reliable and reproducible data.
However, to test a material in a flow porometer, samples are normally cut from the bulk material, which results in damage to the material. This also restricts the number of tests that can be performed on the material. The test involves loading the sample in the sample holder, sealing the sample to prevent leakage, measuring differential pressure and gas flow rate through the dry sample, wetting the sample, measuring differential pressure and gas flow rate through the wet sample and unloading the sample. Consequently, test time is often considerable and operator skill is important.
Therefore, there is the need in the art for a sample holder that overcomes the shortcomings of the prior art. More specifically, there is a need in the art for a fully automated sample chamber, which allows a sample to be loaded without cutting the bulk test material, and allows testing to be repeated without removing the bulk material. There is also a need in the art for sample chambers that prevent any leak due to radial gas flow through the sample, permit automated application of adequate pressure on o-rings to avoid leak and reduce test time, allow automatic sample wetting for reducing test duration, and permit measurement of pressure of turbulent free gas close to the sample to improve accuracy.